> I cannot build something cheaper, or make it more effective than a commercially available product.

Not sure what you are looking to do, but there are plenty of inexpensive radio designs. Consider the Pixie or the SMT version, the Knight SMiTe, either can be built very cheaply.

Onr could also put an amplifier on inexpensive IMS chips for really inexpensive radio projects.

A Raspberry Pi Zero can be bitbanged into a transciever using PWM and SDR and can operate pretty much any mode. It's a very noisy, low power output signal and will need filtering and amplification. Still better than a spark gap transmitter, the ultimate low cost radio.

For cheap recievers, look into foxhole radio designs.